Stencil screen-printing, or silk-screen printing as it is sometimes called, is widely used to impress decorative images on paper or canvas in art work, or on metal or ceramics in industrial operations such as the manufacture of dishware.
In this technique, a permeable image is formed on an otherwise non-permeable cloth. The permeable image portion of the cloth permits the ink to flow through to the substrate beneath, while the non-permeable portion holds the ink back. The ink is ordinarily forced through the permeable image portion by pressure applied with a squeegee.
In industrial screen-printing operations, the printing is customarily done with a machine in which the image-bearing cloth is mounted on a square or rectangular frame. Ink is placed in this frame and a straight, rigid squeegee is then automatically swept over the screen, squeezing the ink through the permeable image portion of the screen and on the work.
Such apparatus is obviously unsuited for decorating work which requires a round or irregularly shaped frame. When used with such a frame, the rigid squeegee cannot reach the far edges of the screen because its ends become locked against the side of the frame as the squeegee stroke proceeds from the center of the frame to the sides. This may leave a portion of the permeable image portion of the screen without ink.
An apparatus has been developed which uses a flexible blade held by several swivelly mounted clamps actuated by chains and cams which bend the blade into an arc as it goes through its lateral stroke and straighten it as it returns to the center. This permits the squeegee to reach the periphery of the screen and allows the entire image area to be covered. Such an apparatus is the American Dubuit Silk Screen Printer, sold by the American Screen Printing Equipment Co., of Chicago, Ill.
This apparatus generally works well, but is complex and costly. Moreover, each frame size, with some tolerance, requires a different squeegee with its own set of cams, so much time is lost in removing cams and installing others when the frame size is changed. Furthermore, the apparatus, because of its bulk, cannot be used to impress images on work having high sides, such as deep dishes or saucepans.
In contrast, the squeegee of the invention is simple, inexpensive, easy to remove from and install in screen printing machines, and, because of its small size, can be used to great advantage on "deep" work. In addition, when frame sizes are changed, the only thing required is replacement of the original squeegee with a larger or smaller one of the same design.